Taiwan’s defence minister warned Tuesday that threats from China were growing daily after Beijing’s aircraft carrier and a flotilla of other warships passed south of the island in an exercise as tensions grow.

After sailing south of Taiwan itself, the Liaoning and five other warships on Monday passed the Taiwan-administered Dongsha Islands in the South China Sea also claimed by Beijing, according to Taiwan’s defence ministry.

The navy drills are seen as a show of strength by Beijing as its relations worsen with Taiwan and the United States, following a protocol-breaking telephone conversation between Taiwanese President Tsai Ing-wen and US President-elect Donald Trump.

Chinese media had earlier reported that the aircraft carrier and escorts were headed for the Pacific on exercise for the first time.

It was the latest in a series of recent exercises staged by China, after its military aircraft passed near Taiwan on December 10 for the second time in less than a month.

Taiwan’s defence minister Feng Shih-kuan had called the timing of China’s air exercises a coincidence, but warned that the island still faces a military threat and called on youths to join the army.

Feng said Tuesday, during a promotion ceremony for generals, that threats from the enemy were growing daily.

“I ask for strict training … We train the soldiers so they can not only survive the war but also destroy the enemies and accomplish their missions,” he said, without referring to China by name.

“The threat from our enemy is increasing day by day. We need to maintain combat vigilance at any time. This is my expectation of you all.”

Feng confirmed that Taiwan sent RF-16 reconnaissance aircraft to monitor the Chinese warships, which were spotted on Sunday some 20 nautical miles outside Taiwan’s air defence identification zone, in the Bashi Channel between Taiwan and the Philippines.

Ties between Taiwan and China have turned increasingly frosty since Tsai’s election victory in January. Beijing has cut off official communication with her government, which took office in May, after it refused to publicly accept the “one China” concept.

Under Taiwan’s previous government the two sides had stuck to the “1992 consensus”, in which they agree there is only one China without specifying which is its rightful representative.

China poses the main military threat to self-ruled Taiwan. Beijing sees the island as part of its territory awaiting reunification — by force if necessary — even though the two sides have been ruled separately since the end of a civil war in 1949.

It has more than 1,000 missiles aimed at the island, according to Taiwan’s defence ministry.